1. Field of the Invention
The present invention relates generally to a method for inserting interbody spinal fusion implants, and in particular to a method for inserting spinal fusion implants configured to restore and maintain two adjacent vertebrae of the spine in anatomical lordosis.
2. Description of the Related Art
Interbody spinal fusion refers to the method of achieving bony bridging between adjacent vertebrae through the disc space, the space between adjacent vertebrae normally occupied by a spinal disc. Numerous implants to facilitate such a fusion have been described by Cloward, Brantigan, and others, and are known to those skilled in the art. Generally, cylindrical implants offer the advantage of conforming to an easily prepared recipient bore spanning the disc space and penetrating into each of the adjacent vertebrae. Such a bore may be created by use of a drill. It is an anatomical fact that both the cervical spine and the lumbar spine are normally lordotic, that is convex forward. Such alignment is important to the proper functioning of the spine. Commonly, those conditions which require treatment by spinal fusion are associated with a loss of lordosis.
Michelson, in U.S. patent application Ser. No. 08/396,414, entitled APPARATUS AND METHOD OF INSERTING SPINAL IMPLANTS, teaches a method for restoring the anatomical lordosis of the spine while performing the interbody fusion procedure. While this has been a significant advance over prior methods, it has nevertheless been associated with a sometimes less than desirable consequence, that being the uneven removal of bone from each of the adjacent vertebrae relative to the vertebral endplates adjacent the disc space.
Therefore, there exists a need for spinal fusion implants and instrumentation that permits for the uniform depth of bone removal from each of the adjacent vertebrae while restoring anatomical lordosis.